[vsnet-chat 5776] Re: [AAVSO-DIS] survey, pixy etc

[Brian Skiff <Brian.Skiff@lowell.edu>]

     I found very recently that there is indeed a paper by Johnson where
he actually says that the observations define the R,I and redder colors.
It is:

1964BOTT....3..305J
  JOHNSON H.L.
  Bol. Obs. Tonantz. Tacub., 3, 305-324 (1964)
  The colors, bolometric corrections and effective temperature of the bright
    stars.

Jean-Claude Mermilliod has a file with the UBVRI part of the data here:

http://obswww.unige.ch/gcpd/cgi-bin/getStars.cgi?Ref=3&Photo=08

In the abstract to the paper Johnson states in part:

     "Data for a total of 256 stars are given in this paper; of these 241 have
complete observations in U,B,V,R,I,J, and K.....  For the R,I,J,K,L,M, and N
systems, the data here should be regarded as the standard values for
additional photometric work."

     However, one should note the systematic problems with V-R and R-I as
a function of _Right_Ascension_, with star color, and with reddening for hot
stars.  This in addition to the large accidental errors (~0.03 to 0.04 per
star) make it a rather poorly defined system.  See Barry et al 1977
(1977ApJ...212..462B) for discussion of the large internal errors, also
Kunkel & Rydgren (1979AJ.....84..633K).  The problems with the RA errors
was found by Cousins himself (1981MNSSA..40...37C).  Finally, se Taylor's
more thorough analysis of the problems in 1986ApJS...60..577T.

\Brian

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